The Geology of Pacific Northwest Volcanoes, Mountains and Earthquakes
Final Study Guide
Seismology
What is a fault scarp? What is the epicenter of an earthquake? What is the hypocenter (or
focus) of an earthquake? What is earthquake magnitude? How is it calculated? What is
earthquake intensity? What is the Modified Mercalli Intensity scale? Which has a larger
intensity, I or XII?
Geomorphic Provinces:
What is geomorphology? Why are ecoregions based upon geomorphic provinces? Where are
the different Geomorphic Provinces of Oregon located? What are the different processes that
formed the different geomorphic provinces (list the provinces and state the processes
responsible for their formation)? Where are the oldest rocks in Oregon found?
Volcanoes:
What types of volcanoes are in the Cascades? What relative Silica content (high, med, or low)
are associated with each of these types of volcanoes? Why does the Silica content control the
behavior of lava flow? Why does the Silica content control the shape of volcanoes? What type
of rock is associated with the different levels of Silica (four types of rock, rank them from low to
high Si %)? What is the timeline of events that led to the eruption of Mt. Saint Helens? What
happened during and after the eruption of Mt. Saint Helens? How were the different lakes
formed around Mt. Saint Helens? Where do we find volcanoes? Why are volcanoes found in
these places? What are some volcanoes associated with the Cascadia subduction zone? Which
Cascade volcanoes erupt more frequently than others? What are some hazards associated with
volcanic eruptions? What controls the type of volcanic eruption, the shape of volcano, and the
way that lava flows? Which lava/rock type is associated with which of these volcanoes: fissure
flow, shield volcano, stratovolcano, lava dome, caldera?
Columbia River Basalts:
What was the geologic event that initiated the eruption of the CRBs? What is the time span for
the CRB eruptions? Where is the source of these lava flows? Where did they flow to? What
causes columnar jointing? What are the processes that create the stratigraphy of a flood basalt
(there are 5 parts, from bottom to top: pillow basalt, lower colonnade, entablature, upper
colonnade, vesicular basalt)? Could you label these parts if you saw a drawing of a flood basalt?
Why do we think there are pillow basalts in the CRBs?
Basin and Range:
What are the processes that led to the Basin and Range (B&R)? How are basins and ranges
formed? What are the geological terms for Basins and Ranges? What type of faults are
associated with the B&R?
The Geology of Pacific Northwest Volcanoes, Mountains and Earthquakes
Final Study Guide
Exotic/Accreted Terranes:
What are exotic terranes (aka
accreted terranes)? Where are
these found in Oregon? What
are the two accreted terrane
geomorphic provinces that we
discussed? When did these
terranes get accreted? If you
saw the following drawing
without labels, could you tell
which terrane were the oldest?
What are the processes that led
to the formation of Siletzia?
Where was the subduction
zone before/during and after the formation of Siletzia?
Rivers and Floods:
What are some factors that contribute to floods? What is a drainage basin/watershed? What is
river discharge? What is a hydrograph? How can we measure discharge (directly or indirectly)?
Why are urban hydrographs more “flashy?” What is a stage-discharge rating curve? Could you
use a river stage with a stage-discharge rating curve to estimate the river dishcharge?
Geologic Maps:
What is a geologic Formation (what are the two parts of this definition)? What is a geologic
contact? What is the strike? What is the dip? What is an anticline/antiform? What is a
syncline/synform? Can you identify the different symbols for strike and dip (including vertical
and horizontal beds), anticline/antiform, and syncline/synform? Can you use the rule of Vs to
interpret the dip of a geological Formation? In what direction does the V point?